Method of orienting cans

ABSTRACT

A method of orienting cans on a continuously rotating machine, in which the machine has a plurality of rotating heads for can bodies (2), each of the heads having a sensor (9) for detecting the orientation of the can body. Each head comprises a mandrel (6), chuck (8) and can carrier (7). In one embodiment, the chuck and mandrel rotate at different speeds. The can body is generally held by the chuck but is transferred to the mandrel in order to impose the required orientation on the can body. In an alternative embodiment, each chuck is driven by an independent motor (15) and orientation is achieved by imposing a motion profile on the chuck to correct any error. An unique mark or series of marks is provided at or around a free edge of the can body so that the sensor can detect the orientation of the can body. Typically these marks are hidden in the finished product by a double seam which joins the can end to the can body.

BACKGROUND OF THE INVENTION

This invention relates to orientation of cans and, in particular, to theorientation of cans which are to have a textured finish which shouldpreferably be registered with the can print, side seam or otherfeatures. Such cans may include food cans, beverage cans or aerosolcans, and may be drawn and wall-ironed (DWI), drawn and redrawn (DRD) ormay have welded bodies.

One example of texturing is known as "roll-forming", in which cans areplaced on a profiled mandrel and are rolled between the mandrel and acurved rail. A single revolution of the can is required to form thedesired textured finish. This texturing method is described inparticular in GB-A-2251197, where the mandrel is profiled with flutes sothat the can body is deformed into the fluted configuration of themandrel during the roll-forming operation. Alternatively, texturing maybe achieved by forming the can between a hard profiled rail and amandrel of elastomeric material. The textured or fluted finishes whichcan be obtained by such roll-forming is aesthetically pleasing but wouldbe further enhanced if such texturing could be formed in register withprint or other surface features on the can body.

GB-A-2077684 describes an apparatus for aligning bottles which have amark in the form of a black line on the bottle neck. The apparatus usesa starwheel with spaces for the bottles, each space having a belt whichengages and rotates the bottle and prevents the bottle from rotatingfurther when the black line is detected. Such a system is not viable forregistration at line speeds of the order of 1000 containers per minuteand cannot align the containers with an accuracy of up to 0.5 mm+0.25 mmwhich is desired by present day can manufacturing lines. Furthermore,the black mark used in GB-A-2077684 would still be visible in the finalproduct.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a method oforienting cans comprising: providing at least one unique mark at oraround a free edge of each can body; scanning at least a section of theunique mark with a sensor; and correcting the orientation of each canbody in accordance with positional data obtained by the scanning step;in which the unique mark is provided in such a position that, in use,when the can body is closed by a can end fixed to the can body aroundthe free edge, the unique mark is covered.

In the present invention, when the can end is joined to the can body bya double seam, for example, the mark is therefore invisible. Since themark is hidden, it will not detract from the appearance of decoratedflutes, texturing, or other roll-formed feature. In addition, the use ofa unique mark enables registration to be achieved independently ofchanges in the design or pattern of the can.

The unique mark may comprise a series of sets of markings which extendaround the whole of the periphery of the free edge so that at anyposition of the can, at least one set of marks can be scanned todetermine the orientation of the can.

Each set of markings, or code sector, may comprise a start sector markfollowed by a binary code and, in a three piece can, preferably includesa weld sector. The start sector mark defines the start of the sector andthe binary code represents the position on the can body e.g. relative toa welded seam in a three-piece can. Alternative marking methods may beused, if preferred, such as lettering or pictorial data but these may beless satisfactory due to high speed of the machine and the time requiredto process such a form of data. Furthermore, the type of sensor requiredto read data of this type may be more complex and expensive.

The method may be used for either two or three piece cans. The uniquemark may be provided in an independent operation or, more preferably, itmay be printed together with the actual decoration of the container fora two piece container or in a sheet from which a three piece containeris to be formed.

According to a further aspect of the present invention, there isprovided a decorated roll-formed container, comprising a roll-formedbody and an end fixed to the body by a double seam, in which the bodyincludes at least one unique mark beneath the double seam whereby thedecoration is registered to the roll-formed features.

According to another aspect of the present invention, there is provideda method of orienting cans on a continuously rotating machine, themethod comprising:

providing a unique mark on each of a plurality of can bodies;

feeding the can bodies to the continuously rotating machine;

engaging each can body on a respective chuck;

rotating the can body at a first speed;

moving the can body axially over a mandrel rotating at a second speed;

providing a sensor for each can body position on the turret;

sensing the position of each can body by detecting its unique mark;

repeatedly verifying the position of each can body by detecting a seriesof non-unique marks;

evaluating the required position of each can body;

comparing the sensed position of each can body with the requiredposition; and

correcting the orientation of each can body.

Continuous measurement of can orientation is possible with the method ofthe present invention since individual sensors are provided for each canposition. There is thus no need for sophisticated data analysis or forthe unique mark to be in the form of binary code markings as would benecessary if, for example, a single camera were used instead of severalsensors. A unique mark or regular mark spacing with a unique mark andsimple counting of marks over a maximum of one revolution is all that isrequired. Even the use of a plurality of sensors in the presentinvention is a fraction of the cost of a single CCD camera which wouldalso require a separate light source of consistent quality.

According to this aspect of the present invention, the unique mark maybe a single mark on the can body, or it may be a different mark in aseries of otherwise identical regularly spaced marks. The unique markmay be different by being a longer mark which may be obtained whereprinting of marks around the circumference of a can body overlaps.Alternatively the unique "mark" may be a gap in the regular marks, i.e.the absence of a mark. Typically, a series of light and dark marks areprinted around the top edge of the can body, where these will ultimatelybe hidden by a seam when an end is seamed onto the can body. The uniquemark specifies absolute angular position of the can body once perrevolution, whilst the regular marks specify a position relative to theunique mark.

The sensor is preferably positioned to detect the unique mark both atthe beginning of the forming process and, advantageously, also at theend of the forming process. The unique mark may be positioned such thatit will be hidden by a seam when an end is seamed onto the can body or,alternatively, a single mark may readily form part of the decoration onthe can body.

Once the can is in the correct orientation, registering with roll-formedfeatures is possible. The method therefore preferably further comprisesa forming or "texturing" step after orientation has been corrected.Furthermore, the method may provide data for quality control in additionto orientation, if registration of can features and texturing ismonitored after forming.

The provision of chucks which engage each can body in addition to theplurality of mandrels enables orientation of the can body to becorrected in different manners. For example, in one embodiment, thefirst and second speeds are different and the correcting step comprisescalculating a transfer time from the difference between these speeds andthe required change in orientation; and transferring the can body fromthe chuck rotating at the first speed onto the mandrel rotating at thesecond, different speed, after the transfer time has elapsed, wherebythe can body is correctly oriented.

The can body may be retained on the chuck by a partial vacuum. In thefirst embodiment, a vacuum is "supplied" to either the chuck or themandrel. The transfer is thus achieved smoothly at maximum speed.Preferably, the can then remains on the mandrel until texturing startsand throughout the forming process. After texturing, the can body may betransferred back onto the chuck which assists in keeping the can body inthe can carrier while it is moved off the mandrel ready for discharge.

In an alternative embodiment, the first and second speeds are initiallythe same and the correcting step comprises calculating and imposingvariations in the speed of the chuck and/or mandrel to provide therequired orientation. The chuck may be driven in this embodiment by amotor, the speed of the motor being varied in order to vary the chuckspeed. A control system may be used to calculate a series of motor speedvariations, known as a motion profile, which provide the necessaryre-orientation before forming starts.

In a further embodiment, the first and second speeds are initiallydifferent and an accelerating motion profile is applied to the chuckand/or mandrel in order to provide the necessary re-orientation for thecan. Generally, the chuck speed is increased until it is in line withthe mandrel speed, as determined by the control system.

When the speed of the chuck is varied to provide orientation, it isnecessary during forming to prevent the motor fighting the mandrel forposition of the can, the mandrel and a curved rail being used to carryout the texturing process. This may be achieved by allowing the motor to"freewheel". Alternatively, a clutching or slipping clutch operation maybe used.

In a beading or texturing operation, a stack of can bodies is introducedat one side of a frame. A turret is driven about the frame with aplurality of mandrels mounted around the turret for rotation on axlesfixed to the turret. Each can body is loaded into a can carrier whichmoves the can body onto a mandrel. In the present invention, a chuck isalso provided so that the can carrier moves both the chuck and the canbody.

In order to texture the can body, the can body rolls on the mandrel overa forming rail, the can body thereby obtaining a profile which may beprovided either on the mandrel as described in GB-A-2251197 or on theforming rail itself, or on both the mandrel and the forming rail.

In accordance with the present invention, a sensor and actuator may befixed to the rotating turret adjacent to each of a plurality of heads,corresponding to each can carrier, chuck, can body and mandrelcombination. Thus, as the machine turret rotates, the can body is at afixed distance from the sensor and is rotating relative to it.Alternatively, a sensor may be fixed to each can carrier. Although thecan carrier moves relative to the turret, the can body remains at afixed distance from the sensor, rotating relative to the sensor, sincemovement of the can carrier is axial only.

Generally, the method comprises registering can body orientation asdetermined by the sensor until forming/texturing starts. Preferably,registering is continuous throughout the forming step but may beinterrupted by the forming and restarted immediately after forming hasbeen completed. The method may further comprise calculating andrecording any error in the orientation after forming has taken place.This gives an indication of how accurately texture length matchesdecoration on the can body. If the error signal is outside apredetermined tolerance, the can body may be automatically rejected.

Further advantages in the calculating of any error between orientationbefore and after forming are that the measurements may be recorded forstatistical analysis and the mean value of the orientation error at thestart of forming may be used to improve the orientation of future canbodies passing through the machine. Alternatively, the error may bedisplayed or otherwise transmitted to an operator so as to indicate thatthe machine requires adjustment. Variability in the orientaton error maybe used as a measure of process capability and used to trigger an alarmas an early warning of machine faults.

According to a further aspect of the present invention, there isprovided an apparatus for roll-forming cans with registered decoration,the apparatus comprising:

a frame; a turret driven to rotate about an axle fixed to the frame; aplurality of mandrels mounted around the turret for rotation on axlesfixed to the turret; a plurality of chucks for driving can bodies; meansfor rotating each chuck at a first speed; means for rotating eachmandrel at a second speed; a plurality of sensors, one for each canbody, for detecting orientation of the can body; and means for varyingthe speed of rotation of each can body whereby the orientation of thecan body is corrected.

Different embodiments may include registering the decoration so as tohave different colors on individual flutes, providing script aroundfolded or textured areas, or simply orienting the decoration to thefront of a welded can so that the decoration is always centrallypositioned.

The roll-formed features may comprise fluting, texturing or folding forexample, and decoration may be aesthetic or functional as desired. Itwill be appreciated that the invention is not limited in any way by thenature of the roll-formed features or by the decoration applied.

Preferred embodiments of the method will now be described, by way ofexample only, with reference to the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial front view of an apparatus for orienting a can body;

FIG. 2 is a side view of a can carrier and can prior to feeding onto amandrel;

FIG. 3 is a side section of a can after feeding onto a mandrel;

FIG. 4 is a schematic of orientation control;

FIG. 5 is a unique mark comprising a series of coded sectors; and

FIG. 6 is a formed can body with coded sectors.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an apparatus for roll-forming a series of can bodies 2 withtextured features in the can side wall. The apparatus 1 comprises astarwheel 3, for separating the cans on entry and a discharge wheel 4,one on either side of a frame. A turret 5 is driven to rotate about theframe and sixteen mandrels 6 are mounted about the turret for rotationon axles fixed to the turret.

References A, B, C, D and E are used to indicate the various stages oforienting and texturing. The can bodies are fed into the machine at Avia star wheel 3 and each can body is loaded in turn into a can carrier.A vacuum chuck then engages the can body and the can body and chuck aremoved axially onto a mandrel between positions A and B.

In one embodiment, sensing of the can position and correction oforientation occurs between B and C. In a second embodiment, where thecan does not need to be in position on the mandrel for orientation tooccur, the sensing and orientation correction may take place from justafter position A, when the chuck has engaged the can body.

Can forming occurs between positions C and D, one revolution beingrequired in order to complete the forming operation. A hard texturedrail is thus located between C and D and the can body is pinched betweenthis hard rail and a soft mandrel, typically of elastomeric material, inorder to achieve the desired textured finish. In an alternativeembodiment, a soft smooth curved rail and a hard profiled mandrel may beused.

In the first embodiment, the can body is simply moved off the mandrelbetween positions D and E, whereas in the second embodiment, orientationmay be checked during this rotation also.

Finally, the can bodies are discharged from the turret at position E.

FIG. 2 is a side view of the can body 2 mounted in a can carrier 7 priorto moving the can onto mandrel 6. The can body is engaged at its base bya vacuum chuck 8. In this arrangement a sensor 9 is fixed to the cancarrier for monitoring the position of the can. The sensor 9 is aphotoelectric device which looks at a unique mark, for example in a codestrip 10 around the top edge of the can.

The code is hidden in the finished article by a double seam, when a canend is seamed onto the can body. A possible design of hidden code isdescribed below with reference to FIGS. 5 and 6. The code describedbelow is, however, more complex than is essential when using individualsensors since only a single unique mark, or regularly spaced marks witha single longer mark or similar indicator is necessary when continuoussensing is used. At most the can body needs to rotate a full revolutionbefore this unique mark is seen.

FIG. 3 shows the can 2 in position over mandrel 6 and engaged by chuck6. Compressed air or a vacuum is applied to the mandrel via line 11 andto chuck 8 via line 12. In the embodiment shown, the chuck is driven bya ring gear 13 via a pinion while the mandrel is driven by ring gear 21via another pinion. The different diameters of the two pinions (that forthe chuck being of larger diameter than that for the mandrel) means thatthe speeds of rotation of the mandrel and chuck are different althoughboth constant, while the turret rotates at constant speed.

Orientation is achieved by transfer from the chuck to the mandrel at aparticular point in the rotation cycle. This type of clutching system isinexpensive and extremely robust although it achieves its best accuracyat low speed. A control system is situated as shown generally at 14, onecontrol system being typically used to control orientation of two cans.There are thus eight control systems required for control of sixteen canpositions around the turret.

In an alternative embodiment, the chuck is driven independently of thering gear, by a single motor mounted on the end of the shaft asindicated by the dotted lines 15. This system of individual motors doesnot need any extra mechanical drive and its accuracy is independent ofthe production speed but in comparison with the clutching system, thismethod is relatively expensive, due to the need for individual motorsand controls.

FIG. 4 shows a block diagram of the orientation control, using aclutching system. In this system, the transfer from the chuck to themandrel for orientaton is achieved by the switching on and off of airlines 11 and 12 which supply the mandrel and chuck respectively.

A switching mechanism 20 acts as both a compressed air and a vacuumgenerator, as required for the can retention or release. Thus whilst therequired position of the can body is being evaluated, the can body isretained on the chuck by a vacuum switched to line 12 and may be furtherencouraged by the application of compressed air to line 11. Once thetransfer time and the required orientation have been determined, the canbody is transferred from the chuck to the mandrel by switching line 12to compressed air and line 11 to vacuum. These lines may be switchedindependently if desired. A small clearance of typically 0.1 mm isprovided between the chuck and the mandrel to enable the can to betransferred from one to the other.

The switch 20 comprises a manifold which receives a single air supply 16from a fixed part of the frame via bearings rotating on the shaft. Theswitch 20 then switches the air lines for each of the 16 heads aroundthe turret in accordance with control signals from each control system14.

Control is provided by eight systems 14 positioned around the turret.Space constraints limit the number of control systems to one for twoheads. An encoder 22 connected to a fixed shaft ensures that correctorientation is achieved independently of the head position around theturret, positional data being received by each control system 14 fromtwo sensors 9 relating to the heads which that system controls.

Each control system thus receives data from a pair of sensors 9,relating to the position of their respective can bodies, as well asencoder data 22 and power 24. This is then used to provide theappropriate actuation of the pneumatic switches 20 and user information26 for quality control, set up etc. Where a single motor for each chuckis used, the actuation signals will again be provided by control system14.

In another embodiment a can body is formed from a metal sheet which hasfirst been printed and onto which code sectors, as shown in FIG. 5, havesimultaneously been printed. The sheet is cut into strips which arewelded into can bodies in known fashion, typically with the codedsectors within 3.2 mm from one free edge of the flanged body on thelower can side wall.

FIG. 5 shows typical series of code sectors for printing around theupper and lower edge of a can body, generally in a position which wouldbe covered by a double seam, once the end is seamed onto the body. Thisset of code sectors comprises 16 code sectors but it will be appreciatedthat this number can be varied according to the can circumference,sensitivity of the measuring equipment, the data required in order toanalyze the position etc. However, it is usual that the sensor will needto see at least two sectors (two code sectors or a code and a weldsector) so as to see at least one whole sector in its field of vision,although this is not a particular issue when continuous monitoring byindividual sensors is used.

At the left hand end of the drawing there is an unprinted weld sector,which in use will contain a weld in a three piece container. This weldsector also includes a white marker, with two black bars either side ofthis which signifies the presence of a weld to the left of the marker,so that the sensor does not take a false reading at this point.

Each of the sixteen code sectors follows the format of a white "start"sector marker and a binary code made up of white/black marks to signify0 or 1 in the binary code. There are three marks making up this binarycode, so that the code can be from 000 (decimal 0) to 111 (decimal 15)according to the sector number, thus having a code for each sector. Ifadditional sectors are required, then more marks will also be needed.

The whole strip of code sectors shown in FIG. 5 is the length of the canoutside circumference, so that the whole can upper edge is marked. Thisensures that the sensor will always see at least part of the code.

The binary code in the example of a three piece 73×115 mm food can isposition within 4.6 mm from a free edge of the can blank, which is then3.2 mm from the edge of the flanged body, and is then covered during theseaming operation by the seam which extends 3 mm from the top or bottomof the finished can.

The codes shown in FIG. 5 are particularly adapted for use with a threepiece welded can. Clearly a two piece can would not require a weldsector, there being no weld. A typical food can including a code sector,prior to the seaming operation is shown in FIG. 6.

Other embodiments are envisaged within the scope of the presentinvention, including two piece cans made by drawing and wall-ironing,draw-redraw operations or impact extrusion processes.

It will be appreciated that the invention has been described by way ofexample only and that changes may be made without departing from thescope of the invention as defined by the claims.

We claim:
 1. A method of orienting cans on a continuously rotatingmachine, the method comprising:providing a unique mark on each of aplurality of can bodies (2); feeding the can bodies (2) to thecontinuously rotating machine; engaging each can body (2) on arespective chuck (8); rotating the can body (2) at a first speed; movingthe (an body (2) axially over a mandrel (6) rotating at a second speed,the second speed being different from the first speed; providing sensor(9) for each can body position on the machine; sensing the position ofeach can body (2) by detecting its unique mark; evaluating the requiredposition of each can body (2); comparing the sensed position of each canbody (2) with the required position; and correcting the orientation ofeach can body by calculating a transfer time from the difference betweenthe first and second speeds and the required orientation; and, after thetransfer time, transferring the can body (2) from the chuck (8) rotatingat the first speed onto the mandrel (6) rotating at the second,different speed, whereby the can body (2) is correctly oriented.
 2. Amethod according to claim 1, further comprising continuously sensing theposition of each can body by detecting and counting a series ofidentical marks (10).
 3. A method according to claim 2, in which thetransferring step comprises switching a vacuum from the chuck to themandrel, whereby the can body is released from the chuck and pulled ontothe mandrel.
 4. A method according to claim 2, in which the sensor (9)is fixed to a turret (5) or to a can carrier (7).
 5. A method accordingto claim 1, in which the transferring step comprises switching a vacuumfrom the chuck to the mandrel, whereby the can body is released from thechuck and pulled onto the mandrel.
 6. A method according to claim 5, inwhich the sensor (9) is fixed to a turret (5) or to a can carrier (7).7. A method according to claim 1, in which the sensor (9) is fixed to aturret (5) or to a can carrier (7).
 8. A method of orienting cans on acontinuously rotating machine, the method comprising:providing a uniquemark on each of a plurality of can bodies (2); feeding the can bodies(2) to the continuously rotating machine; engaging each can body (2) ona respective chuck (8); rotating the can body (2) at a first speed;moving the can body (2) axially over a mandrel (6) rotating at a secondspeed, the second speed being initially the same as the first speed;providing a sensor (9) for each can body position on the machine;sensing the position of each can body (2) by detecting its unique mark;evaluating the required position of each can body (2); comparing thesensed position of each can body (2) with the required position; andcorrecting the orientation of each can body (2) by calculating andimposing variations in the speed of the chuck (8) and/or mandrel (6) toprovide the required orientation.
 9. A method according to claim 8, inwhich the sensor (9) is fixed to a turret (5) or to a can carrier (7).10. An apparatus for roll-forming cans, the apparatus comprising:aframe; a turret (5) driven to rotate about an axle fixed to the frame;and a plurality of mandrels (6) mounted around the turret (5) forrotation on axles fixed to the turret (5); characterized in that theapparatus is for roll-forming cans with registered decoration, and theapparatus further comprises:a plurality of chucks (8) for driving canbodies (2) mounted on the mandrels (6); means (9) for sensing theposition of each can body by detecting its unique mark; means (14) forevaluating the required position of each can body (2); means (14) forcomparing the sensed position of each can body (2) with the requiredposition; means (14) for correcting the orientation of each can body (2)by calculating a transfer time from the difference between the first andsecond speeds and the required orientation; and means (11,12,20) fortransferring the can body from the chuck (8) rotating at the first speedonto the mandrel (6) rotating at the second, different speed, after thetransfer time, whereby the can body (2) is correctly oriented.
 11. Anapparatus for roll-forming cans, the apparatus comprising:a frame; aturret (5) driven to rotate about an axle fixed to the frame; and aplurality of mandrels (6) mounted around the turret (5) for rotation onaxles fixed to the turret (5); characterized in that the apparatus isfor roll-forming cans with registered decoration, and the apparatusfurther comprises:a plurality of chucks (8) for driving can bodies (2)mounted on the mandrels (6); means (9) for sensing the position of eachcan body by detecting its unique mark; means (14) for evaluating therequired position of each can body (2); means (14) for comparing thesensed position of each can body (2) with the required position; means(14) for correcting the orientation of each can body (2) by calculatingand imposing variations in the speed of the chuck (8) and/or mandrel (6)to provide the required orientation.